Filament for thermionic tube



Jan. 8, 1935. w. WEHNERT 1,987,424

FILAMENT FOR THERMIONIC TUBES Filed July 23, 1932 I INVENTOR W-WEHNERT BY ATTORNEY Patented Jan. 8, 1935 UNITED STATES PATENT GFFIfiE FILAMENT FOR THERRIIONIC TUBE Waldemar Wehnert, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a. corporation of Germany Application July 23, 1932, Serial No. 624,252 In Germany August 13, 1931 7 Claims. (Cl. 250-275) In thermionic tubes operating with relatively potential inherent in such an arrangement, large plate currents of the type, for instance, as whence it can be readily seen that the disposition found in the power stages of receiver apparatus of the filament as here disclosed represents a it is customary to use cathodes or filaments comdipole which does not have any efiective outward prising a plurality of parts or sections, the latter action with the result that the desired freedom 5 resulting in forms of arrangement resembling the from humming is secured. letters V, N or W. What is claimed is:

In the drawing Figs. lw-c show these forms of 1. A filament construction for a thermionic filament, and it is also indicated therein in what tube comprising a pair of inverted V-shaped fila- 10 way the filament supply and also the grounding ments arranged side by side in substantially the 10 is effected in these filaments when alternating same plane and electrically connected in series, current is employed by ways and means welland a pair of lead-in conductors connected to the known in the prior art. inner adjacent legs of said filaments for supplying It has been found that in so far as freedom alternating heating current thereto.

from hum is concerned in tubes directly heated 2. A filament construction for a thermionic 1 5 with alternating current, it is solely the v-shaped tube comprising a pair of inverted V-shaped filafilament that will satisfy all requirements, wherements arranged side by side in substantially the as in the case of N- and W-shaped filaments, even same plane, a connection between the outer legs if the potentiometer ground is shifted to an exof the filaments, and a pair of lead-in conductors treme position in either direction, there still reconnected to the inner adjacent legs of said fila- 20 mains an unduly strong humming noise. Exments for supplying alternating current thereto. amining the shape of the potential of the W- 3. A multiple filament for a thermionic tube, shaped filament of Fig. 10, as indicated schematicomprising two pairs of electron emitting porcally in Fig. 2 at right angles to the filament plane, tions, the electron emitting portions of each pair this action will be readily understood for what being connected together only at one of their ends, 25 such a filament represents is a dipole having a one portion of each pair being arranged in close pronounced outward action. proximity and the other portion of each pair being According to the present invention this drawarranged farther apart and electrically connected back is obviated by that in each case the two filatogether, and connections to the closely adjacent ment parts or sections presenting a maximum portions of the filament for supplying alternating 30 potential difference are disposed directly adjacent current thereto. to each other. What is of greatest advantage in 4. A filament construction fora thermionic tube this connection is that the adjacent filament parts comprising four coplanar electron emitting sechave the same fall of filament potential, and that tions, the first and second sections being electrithe cathode parts being geometrically farthest recally connected together at one of their ends, the 35 moved from the median line through the system third and fourth sections being similarly electriconstitute the electrical center of the filament cally connected together at one of their ends, a system. connection between the first and fourth sections By a filament disposition of the kind as disclosed t th Other ends, d do d c rs 0011- in the invention it is feasible also in the case of nected to the second and third sections at their 40 N- and W-shaped filaments to so far minimize Other ends. the residual hum that it will be of about the same 5. A filament for a thermionic tube, comprising order of magnitude as in the V-shaped filament. a plu a ty o S o s e c r a ly Connected in Fig. 3 by way of example illustrates an arrange-' series, and a pair of conductors connected to two ment of a pair of inverted V-shaped filaments, of these sections for connection to an energizing comprising the sections e; f, g and h, the inner source, the arrangement being such that said secsections 5 and or having the lead-in conductors tions which have between them a maximum po- Z and m respectively connected thereto, and the tential difierence are so disposed that they are at outer sections e and it being electrically connected closer proximity to each other than the remain- 59 together in series as shown. With this arrangei Sections a o ea h t er.

ment it will be observed that the maximum po- 6. A filament for a thermionic tube, comprising tential difierence exists between the inner adiaf ur ele tron emit in se i ns le rically concent sections and g and that the outer sections nected in series, and a pair of conductors cone and it constitute the electrical center of the filanected to two of these sections for connection to ment system. Fig. 4 illustrates the shape of the an energizing source, the arrangement being such that said sections which have between them a maximum potential difierence are so disposed that they are at closer proximity than the two filament sections which have between them the 5 least potential difference.

'7. A filament for a thermionic tube, comprising a plurality of sections electrically connected in series and so arranged that the two terminal sections to which the energizing source is adapted to be connected are disposed adjacent one another, and the intermediate sections of the electrical series being disposed farther apart and on either side of the terminal sections.

WALDEMAR WEI-INERT. 

